JP2008304526A - Corona charger and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce downtime made when abnormal discharge occurs in a corona charger equipped with an electrifying means and an electrifying power source. <P>SOLUTION: The corona electrifier includes: a corona discharger SC including a plurality of discharge means WR1 and WR2 opposed to the surface of a body to be electrified PC and having a partition SL between the plurality of discharge means; a plurality of electrifying power sources PS1 and PS2 having a function for supplying corona discharge power to the respective discharge means, a function for stopping the power supply, a function for changing supplied power in accordance with a changing instruction, and a function for restarting supply of the corona discharge power according to release of stop, respectively; abnormal discharge detection means Vs1, Vs2 and Vs3 for detecting the abnormal discharge of the respective discharge means and stopping the power supply of the electrifying power sources PS1 and PS2 for supplying the power to the discharge means which causes the abnormal discharge; and a control means 91 for instructing S332 to increase the supplied power to the other electrifying power source when stopping the power supply caused by the abnormal discharge of one of the plurality of electrifying power sources PS1 and PS2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charging device for charging an object to be charged and an image forming apparatus using the same, and for example, although not intended to be limited thereto, can be used for a printer, a copying machine, and a facsimile.

  For example, a corona charging device used in an electrophotographic image forming apparatus generally has a configuration called a scorotron. A voltage is applied to a wire or sawtooth discharge means, and the flow of electrons jumping out from the discharge means is adjusted by a lattice-like structure called a grid, and the photosensitive member is charged to a constant potential. In the corona charging device, a spark discharge called a leak occurs due to foreign matter adhering to the discharge means and the casing in which it is stored. Also, leakage occurs due to excessive ion retention. When the leak occurs, it becomes impossible to supply sufficient electrons onto the photosensitive member, and the charged potential on the photosensitive member is lowered to cause an image defect. For this reason, in general, the image forming operation of the image forming apparatus is stopped as soon as a leak occurs, and the maintenance person is required to take measures such as cleaning the corona charging device, replacing parts, or replacing the corona charging device itself. Prompt. At this time, the maintenance staff is not always present near the image forming apparatus, and if there is a maintenance staff at a remote location, it takes time until the maintenance of the image forming apparatus, and the image forming apparatus is connected to the corona charging device. Due to the abnormality, the stop time (down time) becomes longer, and the usability of the user is significantly impaired.

  On the other hand, in order to cope with a high image forming speed, it is necessary to increase the charging capability of the corona charging device. Therefore, a method of providing a sub-charging device in addition to the main charging device has been considered and already known.

Japanese Patent Laid-Open No. 2001-13764 JP 2005-338797 A JP 2001-350327 A Special table 2004-505321 gazette Japanese Unexamined Patent Publication No. 2007-041293.

  Patent Document 1 describes a corona charger including a charger wire, a grid, and a cleaning device that automatically cleans them. Patent Document 2 describes a corona charger including two charger wires, a partition between them, a grid, and a grid cleaning mechanism. Patent Document 3 discloses a corona charging device in which a plurality of power supply devices are provided for each of a plurality of discharging means for the purpose of downsizing the corona charging device. In this corona charging device, a power source is connected to each discharge means, and each output is monitored to detect the vibration of the writing wire. When the wire vibration is detected, the discharge output of the wire is reduced by a certain amount.

  In Patent Document 4, the grid voltage of a corona charger having a plurality of corona wires and grids is measured to detect the occurrence of an arc. When an arc occurs, the image forming process is stopped and the standby mode is set to clean the corona charger. An image forming process control is described in which when the apparatus is started and cleaning is completed, the image forming process is restarted from an image frame in which an arc is generated.

  Patent Document 5 discloses a charging method for a photoconductor using a main charging device and a sub-charging device for the purpose of increasing charging capability. This charging method includes a sub-charging device on the upstream side of the main charging device, A configuration is disclosed in which the sub charging device operates according to the electrostatic fatigue state of the main charging device to compensate for the lack of charging capability of the main charging device.

  However, with conventional corona charging devices, in an image forming device with a high image forming speed, the area per unit time through which the photosensitive member passes directly under the corona charging device is large, and the electrons per unit time irradiated per unit area are large. The amount is reduced. For this reason, as the image forming speed increases, the charge amount decreases with the same discharge amount. In order to cope with high speed, the amount of discharge may be increased, but a high-output power source must be a custom product, and the cost is high. Although attempts have been made to increase the charging capability using general-purpose / mass-produced parts, a configuration in which a charging device is prepared for each power source increases the occupied area.

  Provide a corona charging device that supports high output and high speed imaging by using multiple power sources while meeting the demands of low cost and miniaturization by using mass production and general purpose parts that do not have a large output with a single product However, if there is no partition between the discharge means connected to each switching power supply, if the discharge of one discharge means stops, current flows from the other discharge means, and discharge occurs. Since there is a possibility that the switching power supply for starting the discharge of the stopped discharge means restarts, it is necessary to stop all outputs once to restart the discharge. While the output of the corona charging device is stopped, the image forming operation of the image forming apparatus must be interrupted, and there is a problem from the viewpoint of reducing downtime.

  An object of the present invention is to reduce a downtime of a charging function when a discharge abnormality occurs in a charging means in a corona charging device including a plurality of charging means and a plurality of charging power sources connected to the charging means. An object of the image forming apparatus equipped with the corona charging device is to reduce the downtime of the image forming operation when a discharge abnormality occurs in the charging means.

(1) Corona discharger (SC) having a plurality of discharge means (WR1, WR2) opposed to the surface of the body to be charged (PC) and having a partition (SL) between the plurality of discharge means;
Each has a function of supplying corona discharge power to each discharge means, a function of stopping the power supply, a function of changing the power supply according to a change instruction, and a function of restarting power supply of the corona discharge power by canceling the stop. Has multiple charging power supplies (PS1, PS2);
Discharge abnormality detection means (Vs1, Vs2, Vs3) for stopping the power supply of the charging power source (PS1, PS2) for supplying a power to the discharge means in which a discharge abnormality has occurred by detecting a discharge abnormality of each discharge means; and
A corona charging device comprising: a control means (91) that instructs one of the plurality of charging power sources (PS1, PS2) to increase the feeding power (S332) to another charging power source when power feeding is stopped due to abnormal discharge.

  In addition, in order to make an understanding easy, the symbol of the corresponding | compatible element of the Example shown in drawing and mentioned later is attached for reference for the example in a parenthesis. The same applies to the following.

  (2) The discharge abnormality includes a leakage and a voltage abnormality in which no leakage occurs; the corona charging device according to (1) above.

(3) Charge carrying medium (PC);
The corona charging device according to (1) or (2) above, which charges the surface of the charge carrying medium (PC);
A latent image forming means (43) for discharging the charged surface of the charge carrying medium (PC) corresponding to the image data to form an electrostatic latent image of the image represented by the image data;
Means for applying a developer to the electrostatic latent image to develop a visible image; and
An image forming apparatus (MF1) comprising: means for transferring the visible image onto a sheet.

  By having a plurality of discharge means, even if any one of the discharge means is stopped due to a leak or the like, the image forming operation can be continued using only the other discharge means, and there is no sign of leak. If (discharge voltage abnormality) is detected before the leak occurs and the corona charging device is cleaned dynamically, the downtime of the image forming apparatus can be reduced. In addition, effects such as cost reduction and downsizing can be expected.

  By monitoring the discharge voltage of each discharge unit, the state of electrostatic fatigue or dirt on the discharge unit is detected in advance, and the cleaning mechanism is activated before a leak occurs to prevent malfunction of the image forming apparatus. In addition, a decrease in productivity can be minimized by increasing the discharge amount of the discharge means that continues to discharge normally.

  A plurality of discharge means are stored in a space divided by one corona charging device partition (SL), and thus the discharge means are connected to each power source, that is, a plurality of power supplies are supplied to each discharge means. Therefore, it is possible to cope with high-speed image formation with a general-purpose part without preparing a high-output custom-made part, and an image forming operation can be performed even if a discharge abnormality occurs in one discharge means.

  (4) The control means (91) reduces the moving speed of the charge carrying medium (PC) when one of the plurality of charging power sources (PS1, PS2) stops power supply due to abnormal discharge (S333 / S334); The image forming apparatus (MF1) according to (3) above. According to this, when a discharge abnormality occurs in one discharge means and charging is performed using only other normal discharge means, even if the charge amount by the corona discharge device decreases, the charge carrying medium (PC) An appropriate amount of charging can be performed.

  (5) The control means (91) stops the transfer to the paper when the charging power source (PS1, PS2) stops power supply due to abnormal discharge (S35 to S38); Image forming device (MF1).

  (6) When the charging power source (PS1, PS2) stops power supply due to abnormal discharge, the control means (91) creates an image next to the image on which the electrostatic latent image has been formed. (S36 to S38) The step of charging the surface of the charge carrying medium (PC) and the following image forming operation are performed; the image forming apparatus (MF1) according to any one of (3) to (5) above .

  (7) When the designated image forming operation is completed, the control means (91) cancels the suspension of the charging power supply that has stopped power supply due to the discharge abnormality after a set time, and instructs to increase the power supply power. The instruction of the charging power supply is canceled (S521, S53); the image forming apparatus (MF1) described in (6) above.

  (8) The control means (91) drives an air conditioning means (FN) for exhausting the gas of the corona discharger (SC) during the set time (S521); image formation as described in (7) above Device (MF1).

  (9) When the designated image forming operation is completed, the control means (91) drives the cleaning mechanism of the corona discharger (SC) (S522 / S524). The suspension of the charged power supply that has stopped supplying power is released, and the instruction of the charged power supply that has instructed to increase the supply power is released (S53); the image forming apparatus (MF1) described in (6) above.

  (10) The control means (91) interrupts the image forming operation when two or more of the plurality of charging power sources (PS1, PS2) have stopped feeding due to abnormal discharge, and the electrostatic latent The next image after the image formation has been completed is defined as image formation (S41 to S46), and after the set time, the suspension of the charging power supply that stopped power supply due to the discharge abnormality is canceled, and the image formation is performed. The step of charging the surface of the charge-carrying medium (PC) of the defined image The following image forming operation is performed (S65, S58, S59-S9); the image forming apparatus (MF1) described in (3) above.

  (11) The control means (91) drives the air conditioning means (FN) for exhausting the gas of the corona discharger (SC) during the set time (S64); image formation as described in (10) above Device (MF1).

  (12) The control means (91) interrupts the imaging operation when two or more of the plurality of charging power sources (PS1, PS2) are stopped due to discharge abnormality, and the electrostatic latent The next image after the image formation has been completed is defined as an image (S41 to S46), the cleaning mechanism of the corona discharger (SC) is driven (S67), and when the cleaning is completed, the discharge abnormality The charging power supply, which has stopped supplying power, is released from the stop, and the following image forming operation is performed to charge the surface of the charge carrying medium (PC) of the image defined in the image forming (S65, S58, S59-S9). ); Image forming apparatus (MF1) according to (3), (10) or (11) above.

  (13) Any one of the above (3) to (12) comprising communication means (71, 79, 83) for notifying the service center by communication of the occurrence of power supply stop due to the discharge abnormality (S35 / S43) The image forming apparatus (MF1) described in 1.

  (14) The above-mentioned (7) to (7), comprising: communication means (71, 79, 83) that communicates with the service center via communication (S54 / S59) the cancellation of the suspension of the charged power supply that has stopped feeding due to the discharge abnormality. The image forming apparatus (MF1) according to any one of 13).

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  FIG. 1 shows the external appearance of a multi-function full-color digital copying machine MF1 according to the first embodiment of the present invention. This full-color copying machine is roughly constituted by units of an operation board 10, a color scanner 20, an automatic document feeder (ADF) 30, a color printer 40, and a paper feed bank 50. A LAN (Local Area Network) to which a personal computer PCM is connected is connected to the image data processing apparatus in the apparatus. Further, the in-machine facsimile controller FCU 60 (FIG. 2) can perform facsimile communication via the exchange PBX and the public communication network PN.

  The printer 40 includes a transfer unit, and the transfer unit includes a transfer belt 41 that is an endless belt. The transfer belt 41 is wound around three support rollers and one tension roller, and is driven to rotate clockwise. Near the tension roller, there is a transfer body cleaning unit that removes residual toner remaining on the transfer belt 41 after image transfer.

  The transfer belt 41 between one support roller and another support roller is equipped with image forming units for C, M, Y, and Bk color image forming along these moving directions. There is a transfer roller 42 facing each photoconductor drum PC with the transfer belt 41 interposed therebetween. Above the image forming apparatus, there is a laser exposure unit 43 that irradiates each photoconductor drum of each color photoconductor unit with laser light for image formation. Each photosensitive drum PC is uniformly charged by each corona charger SC, and a laser whose unit is modulated with an image signal is projected on the charged surface by a laser exposure unit 43. The developing device develops the electrostatic latent image generated thereby to form a toner image. This toner image is transferred to the transfer belt 41.

  Below the transfer belt 41 is a transport belt 45. The conveyor belt 45 transfers the toner image on the transfer belt 41 onto a sheet. The paper (transfer paper) on which the toner image is transferred is sent out to the fixing unit 46 by the transport belt 45. Below the conveying belt 45 and the fixing unit 46, there is a double-sided drive unit that is a sheet reversing unit that feeds a sheet immediately after an image is formed on the front surface and reverses the front and back to record an image on the back surface.

  When the start switch is pressed, if there is a document in the automatic document feeder (ADF) 30, it is transported onto the contact glass of the scanner 20, and if there is no document in the ADF 30, the manually placed document on the contact glass Immediately, the scanner 20 is driven, and the first carriage and the second carriage in the scanner 20 are read and scanned. Then, light is emitted from the light source on the first carriage to the contact glass, and reflected light from the document surface is reflected by the first mirror on the first carriage and directed to the second carriage, and reflected by the mirror on the second carriage. Then, an image is formed on the CCD 21 (FIG. 2) as a reading sensor through the imaging lens. C, M, Y, and Bk color recording data are generated based on the image signal obtained by the reading sensor.

  Further, when the start switch is pressed, the rotation driving of the transfer belt 41 is started, the image forming preparation of each unit of the image forming apparatus is started, and the image forming sequence of each color image is started. Thus, an exposure laser modulated based on each color recording data is projected onto the photosensitive drum for each color, and each color toner image is transferred onto the transfer belt 41 as a single image by each color image forming process. When the leading edge of the toner image enters the conveyance belt 45, the sheet is fed from the registration roller pair 47 to the transfer belt 45 at a timing so that the leading edge enters the conveyance belt 45 at the same time. The toner image is transferred to the paper. A voltage for transferring toner is applied to the transfer belt 41 by a transfer roller 42. The sheet on which the toner image has moved is sent to the fixing unit 46 where the toner image is fixed on the sheet.

  Note that the above-described sheet is selectively rotated by driving one of the sheet feeding rollers immediately above the sheet feeding trays (also referred to as sheet feeding trays or cassettes) 51 to 53 of the sheet feeding bank 50, so that the sheet feeding bank 50 has multiple stages. The sheet is fed out from one of the paper feed trays 51 to 53, separated by a separation roller, put into a vertically arranged transport roller unit, transported upward, and guided to the transport roller unit in the printer 40 for transport. After abutting and stopping against the registration roller pair 47 of the roller unit, the roller is sent to the conveyor belt 45 at the timing described above. The sheet detection circuit 111 a detects the paper that has arrived immediately before the registration roller pair 47. It is also possible to feed paper by inserting paper on the right side manual feed tray. When the user is inserting paper onto the manual feed tray, the printer 40 rotates the paper feed roller of the manual feed tray to separate one sheet on the manual feed tray and pull it into the manual feed path, and the registration roller Stop against the 47.

  The paper discharged after receiving the fixing process by the fixing unit 46 is guided to the discharge roller by the switching claw and stacked on a paper discharge tray (not shown). Alternatively, it is guided to the double-sided drive unit by the switching claw, reversed there and led again to the transfer position, and the image is recorded also on the back surface, and then discharged onto the paper discharge tray by the discharge roller. The sheet detection circuit 111 b detects the fixed paper that comes out of the fixing unit 46. On the other hand, residual toner remaining on the transfer belt 41 after image transfer is removed by a transfer body cleaning unit (not shown) to prepare for image formation again.

  FIG. 2 shows a system configuration of the electrical system of the multifunction copying machine MF1 shown in FIG. The electrical system includes a controller 70 that performs overall control of the image forming apparatus, an operation board 10 of the image forming apparatus connected to the controller 70, an HDD 78 that stores image data, and communication that communicates with the outside using an analog line. Control device interface board 79, LAN interface board 80, FAX control unit 60, IEEE1394 board, wireless LAN board, USB board, etc. 81 connected to general-purpose PIC bus, engine control 90 connected to controller via PCI bus, An I / O board 100 for controlling I / O of the image forming apparatus connected to the engine control 90, a scanner board (SBU: Sensor Board Unit) 22 for reading a copy original (image), and image data on the drum In It is composed of an LDB (laser diode board) 43 for writing.

  A reading unit 20 that optically reads a document scans the document with a document illumination light source, and forms a document image on the CCD 21. An original image, that is, reflected light of light irradiation on the original is photoelectrically converted by the CCD 21 to generate R, G, B image signals.

  The communication control device interface board 79 immediately notifies an external remote diagnosis device when a failure occurs in the device, and allows the service person to recognize the content and situation of the failure part and repair it immediately. . In addition, it is also used for sending out the usage status of the device.

  The CCD 21 shown in FIG. 2 is a 3-line color CCD that generates R, G, and B image signals of EVENch (even pixel channel) / ODDch (odd pixel channel) and inputs them to an analog ASIC (Application Specific IC) on the SBU board. To do. The SBU board includes an analog ASIC and a circuit that generates drive timings for the CCD and analog ASIC. The output of the CCD 21 is sampled and held by a sample and hold circuit inside the analog ASIC, then A / D converted, converted into R, G and B image data, shading corrected, and output I / F (interface) 23, the image data is sent to an image data processor IPP (Image Processing Processor; hereinafter simply referred to as IPP) 94 via the image data bus.

  The IPP 94 is a programmable arithmetic processing means for performing image processing, including separation generation (determination of whether an image is a character area or a photographic area: image area separation), background removal, scanner gamma conversion, filter, color correction, scaling, and image. Performs processing, printer gamma conversion, and gradation processing. The R, G, B image data transferred from the SBU 22 to the IPP 94 is corrected for signal deterioration (signal deterioration of the scanner system) accompanying quantization into the optical system and digital signal by the IPP 94 (separation generation, background removal, scanner) Gamma conversion, filter) and the frame memory 77. In the case of copying, this image data is read from the frame memory 77 and corrected to image data C, M, Y, B for printer output by the IPP 94 (color correction, scaling, image processing, printer gamma conversion). , Gradation processing), and is output to the LDB 43 of the printer 40.

  The system controller 70 includes a ROM 72 that controls the CPU 71 and the system controller board, a RAM 73 that is a working memory used by the CPU 1, a lithium battery, an NV-RAM 74 that includes an SRAM backup and a clock, and a system controller board 70. The system bus control, frame memory control, FIFO and other ASIC 75 for controlling the CPU periphery, its interface circuit, state change detection circuit ACD and the like are mounted.

  The state change detection circuit ACD includes detection signal lines of the pressure plate switch of the scanner 20 and a filler sensor (document presence sensor) of the ADF 30, a key operation detection signal line of the power key 19 of the operation board 10, and a reception detection signal of the FCU 60. The line is connected. While the main power switch 201 (FIG. 2) is on, the state change detection circuit ACD is applied with the pause activity voltage + 5VE that is continuously output even when the power supply circuit 200 is in the pause mode. As long as + 5VE is applied, if there is a signal change in any of the signal lines connected to the detection circuit ACD, a change detection signal indicating this is given to the CPU 71. In response to this signal, the CPU 71 switches the power supply circuit 200 from the sleep mode to a standby mode (operating mode) in which operating voltages + 5V and + 24V are output to each part of the copier.

  The system controller 70 has functions of a plurality of applications such as a scanner application, a facsimile application, a printer application, and a copy application, and controls the entire system. The input of the operation board 10 is decoded, and the setting of the system and the contents of the state are displayed on the display unit of the operation board.

  Many units are connected to the PCI bus 82, and image data and control commands are transferred in a time division manner by the image data bus / control command bus.

  The communication control device interface board 79 is a communication interface board between the communication control device 83 and the controller 70. Communication with the controller 70 is connected by full-duplex asynchronous serial communication. The communication control device 83 is multi-drop connected according to the RS-485 interface standard. Communication with the remote management system is performed via the communication controller device interface board 79.

  The LAN interface board 80 is connected to an in-house LAN. It is a communication interface board between the in-house LAN and the controller 70, and is equipped with a PHY chip. The LAN interface board 80 and the controller 70 are connected by standard communication interfaces of a PHY chip I / F and an I2C bus I / F. Communication with an external device is performed via the LAN interface board 80.

  The HDD 78 is used as an application database that stores system application programs and device activation information of printers and image forming process devices, and an image database that stores image data of read images and written images, that is, image data and document data. . Both the physical interface and the electrical interface are connected to the controller through an interface compliant with ATA / ATAPI-4.

  The operation board 10 is equipped with a CPU, ROM, RAM, LCD, and ASIC (LCDC) for controlling key input. In the ROM, a control program for the operation board 10 that controls input reading and display output of the operation board 10 is written. The RAM is a working memory used by the CPU. Through communication with the system controller 70, the panel is operated to perform input for the user to input system settings, and display and input control for displaying the system setting contents and status to the user.

  The black (B), yellow (Y), cyan (C), and magenta (M) write signals output from the work memory 76 of the system controller 70 are C, M, Y of LDB (Laser Diode control Board). , B LD (Laser Diode) writing circuit. The LD write circuit performs LD current control (modulation control) and outputs the result to each LD.

  The engine control 90 mainly performs image creation control for image formation, and includes a CPU 91, an IPP 94 for image processing, a ROM 92 containing a program necessary for controlling copying and printout, a RAM 93 necessary for the control, and an NV -RAM95 is installed. The NV-RAM 95 includes an SRAM and a memory that detects power-off and stores it in the EEPROM. The I / O ASIC 96 that also transmits and receives signals to and from the CPUs 71 and 101 that perform other controls and also has a serial interface is a device that is mounted with an engine control board 90 and connected to a nearby I / O. ASIC for controlling (counter, fan, solenoid, motor, etc.). The I / O control board 100 and the engine control board 90 are connected via a synchronous serial interface.

  A sub CPU 101 is mounted on the I / O control board 100 and performs I / O control of the image forming apparatus including analog control such as P sensor and T sensor. Each of the four sets of corona charging power sources PS1 to PS3 supplies corona charging power to each of the four sets of corona chargers SC shown in FIG. The normal / abnormal stop of each of the four corona charging power sources PS1 to PS3 is given to the CPU 91 via the interface 104, and the CPU 91 sends an initialization instruction, an output increase instruction, and other control signals to the interface 104 when necessary. To the corona charging power sources PS1 to PS3.

  As shown in FIG. 3, the operation board 10 includes a key group 12 in addition to the liquid crystal touch panel 11. The key group 12 includes a numeric keypad 13, a clear / stop key 14, a start key 15, an initial setting key 16, a mode switching key 17, a test print key 18, and a power key 19. Alphabets with hiragana added for input, setting and abbreviated registration of URLs, file names, folder names, etc. are displayed on the liquid crystal touch panel 11 with key buttons at their input stages. The power key 19 is an operation key for instructing switching from a sleep mode (low power mode) to a standby mode (operation mode) in which image printing is possible and vice versa. If the power key 19 is pressed once when the sleep mode is set, the sleep mode is switched to the standby mode. When the power key 19 is pressed once in the standby mode, the standby mode is switched to the sleep mode. The test print key 18 is a key for printing only one copy regardless of the set number of print copies and confirming the print result.

  By pressing the initial setting key 16, the initial state of the machine can be arbitrarily customized. It is possible to arbitrarily set a state that is set when the transition time Td1 to the pause mode is set, the paper size stored in the machine is set, or the copy function reset key is pressed. When the initial setting key 18 is operated, a selection button for designating an “initial value setting” function for setting various initial values is displayed. The “transition time Td1 setting” function can be selected to change the transition time Td1. That is, the user can freely set the transition time Td1 from the end or interruption of copying or printing to the switching to the pause mode. One of the selection buttons for designating the “initial value setting” function is an initial setting button of the corona charger SC, and when a user (a user having a management authority or a service person) presses the initial setting button, The operation display board 10 displays an initial setting menu of the corona charger SC on the liquid crystal touch panel 11. In the initial setting menu, specify the charging device operation mode (continuation priority / recovery priority) to be executed when the corona charging power supply stops output (corona charging power supply) due to discharge abnormality, and the corona charger There is a specification of the return mode (simple return / complete return) to be corrected. Although these defaults are “continuation priority” and “complete recovery”, the user operates the menu selection button and the changeover key of the initial setting menu of the corona charger SC, and the operation mode changes from “continuation priority” to “recovery priority”. And the reverse mode can be switched from “complete return” to “simple return” and vice versa. The designated mode is written in the NV-RAM 95 and is maintained while the power is turned off.

  The liquid crystal touch panel 11 displays various function keys, input keys for inputting execution conditions for the selected function, a message, and the like. The LCD touch panel 11 is used to select and execute a “copy” function, a “read” function, a “register” function, an “external memory write” function, a “print” function, an “external memory output” function, and a “facsimile” function. A function selection key representing the inside is displayed. When the user touches the function selection key, an input / output screen determined for the function is displayed on the liquid crystal touch panel 11.

  For example, when the “copy” function is designated, as shown in FIG. 3, a message indicating the function key group, the number of copies, and the state of the image forming apparatus is displayed. In the function key group, print color designation keys “black (BK)”, “full color”, “automatic color selection”, “blue (C)”, “red (M)” and “yellow (Y)” designation There is a key. When the operator touches a key displayed on the liquid crystal touch panel 11, the operation board 10 reads it as an operator input, and highlights the key indicating the selected function in gray indicating that it is being designated. Copying can be performed by setting a document on the scanner 1 and pressing the start key.

  When the user touches the “read” selection key, the document can be read by the scanner 20 and the image data can be transmitted to the PCM directly connected via the network I / F 10 or the PCM that can communicate via the network. The “registration” function registers image data read by the scanner 20 or document information input from the outside (network I / F 10, media I / F 11, etc.) in the HDD 78. The “external memory writing” function reads an original with the scanner 20 and stores it on a removable medium (for example, a memory card) via the media I / F 11. The “print” function is to print out document information registered in the HDD 78 by the printer 40. The “external memory output” function reads out the image data of the image file of the removable media via the media I / F 11 and prints it with the printer 40. The “facsimile” function reads the original with the scanner 20 and transmits it by facsimile.

  FIG. 4 shows a configuration of one set of four corona chargers SC and power supplies PS1 to PS3 that supply a corona charging amount to the one set of corona chargers SC. The configuration of another set of corona chargers SC is also shown in FIG. 4, and one set of power supplies PS1 to PS3 is connected to each set. As shown in FIG. 4, in one set of corona charger SC, the casing CH and the grid GR are electrically connected. Electrons emitted from the first wire WR1 and the second wire WR2 into the air by discharge flow down to the surface of the photoreceptor PC like a shower. When a voltage is applied to the grid GR, if the surface potential of the photoconductor PC becomes equal to the potential of the grid GR, electrons do not reach the photoconductor PC any more, and the surface of the photoconductor PC is uniformly distributed. Charge to potential.

  In order to uniformly charge the surface of the photosensitive drum PC that is a charged body (charged body) and a charge carrier, a voltage sufficient to generate corona discharge in the atmosphere is generated in the corona charger SC. A first wire WR1 which is a discharge means connected to a first power supply PS1 capable of discharging, and a discharge means connected to a second power supply PS2 capable of generating a voltage sufficient to generate a corona discharge in the atmosphere. There is a second wire WR2 and a scorotron grid GR for controlling the flow of electrons toward the surface of the photosensitive drum PC. The grid GR is connected to a third power source PS3 for setting the charged potential of the photoconductor PC to a target potential. In the present embodiment, each of the first to third power supplies PS1 to PS3 generates and outputs a negative voltage. Between the first wire WR1 and the second wire WR2, there is provided a partition SL that is connected to the casing CH of the corona charger SC and prevents a current from flowing between the first and second wires. Further, the casing CH of the corona charger SC and the grid GR are electrically connected. Furthermore, a fan FN (FIG. 1) is provided for cooling the entire corona charger SC and venting the entire apparatus to remove gaseous ions such as ozone generated by corona discharge.

  The first power supply PS1 connected to the first wire WR1 of the corona charger SC is a switching type power supply that performs constant current control, and the first wire WR1 is fed back by feedback of the output current value from the first current detection circuit Is1. In the drive circuit DR1, feedback current value control (constant current control) is performed so that the magnitude of the discharge current from becomes a predetermined value. The first power supply PS1 generates a negative voltage and outputs it to the first wire WR1.

  The second power source PS2 connected to the second wire WR2 of the corona charger SC is a switching type power source that performs constant current control, and the second wire WR2 is fed back by feedback of the output current value from the second current detection circuit Is2. Current feedback control (constant current control) is performed in the drive circuit DR2 so that the magnitude of the discharge current from becomes a predetermined value. The second power supply PS2 also generates a negative voltage and outputs it to the second wire WR2.

  The third power supply PS3 connected to the grid GR of the corona charger SC is a shunt regulator (dropper) type power supply that performs constant voltage control, and the scorotron grid is fed back by feedback of the output voltage value from the voltage detection circuit Vs3. The drive circuit DR3 performs control so that the potential becomes a predetermined value. The third power supply PS3 also generates a negative voltage.

  Since the voltage is generated in the grid GR by using the flow of the discharge current from the first wire WR1 and the second wire WR2 into the grid GR, if both the outputs of the first power source PS1 and the second power source PS2 are cut off The voltage of the third power supply PS3 is stopped. However, it is possible to generate a voltage on the grid GR as long as the discharge of both wires WS1 and WS2 does not stop simultaneously.

  At the moment when a leak occurs in the first wire WR1, as shown in FIG. 9, the discharge current (absolute value) of the first wire WR1 instantaneously shows a significantly large value, and the voltage drops. This is because the first power source PS1 connected to the first wire WR1 is a power source that performs constant current control, so when a leak occurs, it is between the grid GR (or the casing CH and the partition SL connected thereto) and the like. This is because a discharge path is formed, and the resistance value between the first wire WR1 and the grid GR so far decreases, and the voltage decreases as the resistance value decreases according to Ohm's law. The first power supply PS1 detects this abnormal drop in voltage as a leak by the voltage detection circuit Vs1. The drive circuit DR1 of the first power supply PS1 stops the power supply operation in response to the leak detection and enters the stop lock state, and switches the state data of the state data line connected to the interface circuit 104 to the one representing the leak. When the CPU 91 receives an initialization (reset) instruction (stop release) from the CPU 91 to the control data line connected to the interface circuit 104, the drive circuit DR1 releases the stop lock state and responds to the power supply instruction to generate the corona charging power. It returns to the state where power can be supplied.

  Since air has a relatively high electrical resistance value, the first wire WR1 is at a higher potential than the grid GR, but the moment the leak occurs is close to the short circuit between the first wire WR1 and the grid GR. In this state, the voltage of the grid GR slightly increases. However, since the third power supply PS3 connected to the grid GR is a power supply that performs constant voltage control, it quickly settles to a predetermined voltage.

  There are two types of leaks occurring from the first wire WR1. One is that the dust resistance such as paper dust, dust and toner floating in the machine adheres to the first wire WR1, and the discharge resistance increases. As shown in FIG. 10, the discharge voltage of the first wire WR1 ( When the absolute value) increases, that is, due to a high voltage abnormality, the air insulation is destroyed and a leak occurs. This high voltage abnormality is called a high voltage abnormality that is a sign of leakage. The other is that ions generated when electrons emitted from the first wire WR1 by the corona discharge collide with air molecules are between the first wire WR1 and the grid GR (and the casing CH and the partition SL connected thereto). As a result, the electric current flows easily due to the decrease in the insulation resistance of the air, and as shown in FIG. 11, the discharge voltage (absolute value) of the first wire WR1 decreases, that is, the low voltage becomes abnormal and leakage occurs. appear. This low voltage abnormality is called a low voltage abnormality that is a sign of leakage.

  When the voltage detection circuit Vs1 detects that there is a risk of leakage because the discharge voltage (absolute value) of the first wire WR1 has decreased to a predetermined value, that is, when it detects a low voltage abnormality (FIG. 10) as a precursor to leakage. The drive circuit DR1 of the first power supply PS1 stops the power supply operation in response to the detection of the low voltage abnormality, enters the stop lock state, and converts the state data of the state data line connected to the interface circuit 104 to the low voltage abnormality. Switch to something that represents.

  When the voltage detection circuit Vs1 detects that there is a risk of leakage because the discharge voltage (absolute value) of the first wire WR1 has increased to a predetermined value, that is, when it detects a high voltage abnormality (FIG. 11) as a precursor to leakage, The drive circuit DR1 of the first power supply PS1 stops the power supply operation in response to the detection of the high voltage abnormality, enters the stop lock state, and converts the state data of the state data line connected to the interface circuit 104 to the high voltage abnormality. Switch to what you represent.

  The discharge abnormality of the second wire WR2 is the same as that of the first wire WR1, and the configuration and function of the second power source PS2 for supplying the corona charging power to the second wire WR2 are the same as those of the first power source PS1. is there.

  The third power source PS3 connected to the grid GR of the corona charger SC is driven by the drive circuit DR3 so that the potential of the scorotron grid becomes a predetermined value by feedback of the output voltage value from the voltage detection circuit Vs3. Although feedback control is performed, when both the outputs of the first power supply PS1 and the second power supply PS2 disappear, a voltage drop due to this is detected as a discharge abnormality of WR1 and WR2 (PS1 and PS2 stop) by the voltage detection circuit Vs3. In response to the detection of the discharge abnormality, the drive circuit DR3 of the third power supply PS3 stops the constant voltage control operation and enters the stop lock state, and the state data of the state data line connected to the interface circuit 104 is changed to the whole abnormality. Switch to the one representing (PS1 and PS2 stop). When an initialization (reset) instruction is received from the CPU 91 to the control data line connected to the interface circuit 104, the drive circuit DR3 releases the stop lock state and can control the grid voltage in response to the power supply instruction. Return.

  Although not shown, the corona charger SC has a WR1 cleaning mechanism, a WR2 cleaning mechanism, and a GR cleaning mechanism, and each can be automatically cleaned individually.

  FIG. 5 shows an outline of the system control executed in response to a user operation on the operation display board 10 or a command from the PCM by the system controller 70 (CPU 71) shown in FIG. When the operating voltage is applied, the CPU 71 clears the output port, initializes the internal memory and registers (steps S1 and S2), and reads the status of each unit (step S3). Below, the word step is omitted in parentheses and only the step number is written.

  At this time, the CPU 91 of the engine control 90 also reads the state of each part, and then refers to the modification instruction data Cac of the 2-bit configuration of the NV-RAM 95 (S4a), and the charger modification is necessary (one of the two bits of Cac is “1”), and if so, “charger modification” CAD is executed. The contents of the “charger modification” CAD will be described later with reference to FIG.

  If there is an abnormal part or “charger correction” is in an incapable state, the CPU 71 notifies the display 11 or LED of the operation display board 10 and waits for it to change to normal (normal operation is possible) ( S4b, S5). If it is normal, “input reading” (S6) waits for a user operation on the operation display board 10 or a command or reception request from PCM or FAX.

  Here, when the “initial setting” key on the operation display board 10 is operated, the operation display board 10 (the CPU 71 in the operation display board 10) executes “initial setting” (S8). In this “initial setting” (S 8), the operation display board 10 displays an initial setting menu screen on the LCD (liquid crystal touch panel) 11. The menu screen includes an item for user registration, and when the operator designates the user registration, an MF1 administrator password input screen is displayed. When the operator inputs the MF1 administrator password, the operation display board 10 displays a user registration input screen. User registration can be performed by entering a user name and password on this screen. The user registration information (user name & password) is written in the nonvolatile memory of the operation display board 10.

  When the user designates “copy” in the function selection key group displayed on the LCD 11 of the operation display board 10, the display on the LCD 11 becomes a copy mode input screen, and the CPU 71 of the controller SCD displays the user on the operation display board 10. "Copy" (S10) is executed in response to the copy input operation.

  When the user designates “read” in the function selection key group, the display on the LCD 11 becomes an input screen for the original image “read” mode, and the CPU 71 responds to the user's input operation for reading on the operation display board 10. "Read" (S12) is executed. When the user designates “print” in the function selection key group, the display on the LCD 11 becomes an input screen for the stored image “print” mode, and the CPU 71 inputs the user's stored image to the operation display board 10. “Print” (S14) is executed in response to the operation. When the user designates “facsimile” in the function selection key group, the display on the LCD 11 becomes an input screen of the “facsimile (transmission)” mode of the document placed on the scanner 10, and the CPU 71 displays the user's operation on the operation display board 10. “Facsimile” (S16) is executed in response to the input operation for facsimile transmission. When the user designates “accumulate” in the function selection key group, the display on the LCD 11 becomes an input screen of an “accumulate” mode for accumulating (registering) the image of the document placed on the scanner 10 in the HDD 78, and the CPU 71 operates The “accumulation” (S18) is executed in response to the input operation for accumulation by the user on the display board 10.

  The personal computer PCM connected to the multi-function copier MF1 uses the PCM as an operation terminal equivalent to the operation display board 10 and displays a read image on the display connected to the PCM in the same manner as the display of the operation display board 10. An application program is installed, and the user can use the copier MF1 using the PCM in the same manner as using the operation display board 10. By starting the PCM application program, an input screen similar to the operation board input screen displayed on the LCD 11 of the operation display board 10 is displayed on the PCM display. By clicking or pressing the Enter key, the PCM recognizes the input operation for the input button. When a command is sent from the PCM to the controller SCD of the copier MF1 in response to an input operation on the PCM, the CPU 71 of the controller SCD performs a command similar to the case where the input operation is performed on the operation display board 10. The process proceeds to the corresponding control (S19, S20).

  When the external memory, that is, the medium is connected to the external I / F of the board 81, the display on the LCD 11 becomes an input screen for reading / writing data to / from the external memory, and the CPU 71 displays the external display of the user with respect to the operation display board 10. An “external memory application” (S21, S22) that responds to the memory read / write input operation is executed.

  In the charging process of the photosensitive drum PC by the corona charger SC in the above-described “copy” S10, “printing” S14 and other image forming processes in which the printer 40 forms an image on the paper, the corona charging power sources PS1 to PS3 are used. When the power supply is stopped and status data indicating leakage, low voltage abnormality, high voltage abnormality or total abnormality is generated, the interface circuit 104 gives a “charger abnormality interruption” signal to the CPU 91. In response to this interrupt signal, the CPU 91 executes a “charger abnormality interrupt” CAI.

  FIG. 6 shows an outline of the “charger abnormal interrupt” CAI. When proceeding to this, the CPU 91 stores the abnormal state data (leak / low voltage abnormality / high voltage abnormality / overall abnormality) in which the corona charging power source (PS1 to PS3) whose power supply output is stopped is generated in the register Dam (CPU 91). (1 area of the internal memory) (S31), if the power supply (abnormally stopped power supply) that stopped power supply in response to the abnormality is PS1, "WR1 continuation processing" S33, the abnormally stopped power supply is PS2 “WR1 continuation process” S39 is performed, and “imaging stop” S41 is performed when the abnormal stop power source is PS1, PS2, or PS3.

  In “WR1 continuation processing” S33, if it is the “continuation priority” mode corresponding to the operation mode data of the NV-RAM 95, the PS2 is instructed to increase the power supply (S332), and the imaging linear velocity (PC Rotational speed, etc .: sub-scanning speed) is decreased by the set small value (S333). If it is in the “recovery priority” mode, the imaging linear velocity is lowered by the set large value without increasing the output power of PS2 (S334). In the continuous priority mode, increasing the discharge amount of the second wire WR2 increases the possibility of leakage in the second wire WR2, but the image forming productivity during the continuous processing is high. In the recovery priority mode, the image forming productivity is relatively lowered, but it is possible to return to the normal state more safely without increasing the possibility of leakage in the second wire WR2 while continuing.

  While the discharge from the first wire WR1 is stopped, the discharge current of the remaining second wire WR2 is increased, and the image forming linear speed is reduced by a small amount, thereby minimizing the productivity reduction of the image forming apparatus. That is the point. At the moment when leakage occurs in the first wire WR1, the discharge current of the first wire WR1 instantaneously shows a significantly large value, and the voltage drops. This is because the first power source PS1 connected to the first wire WR1 is a power source that performs constant current control, so when a leak occurs, it is between the grid GR (or the casing CH and the partition SL connected thereto) and the like. This is because a discharge path is formed, and the resistance value between the first wire WR1 and the grid GR so far decreases, and the voltage decreases as the resistance value decreases according to Ohm's law. In the first power supply PS1, leakage is detected by detecting this voltage drop by the voltage detection means. The first power supply PS1 that has detected the leak stops outputting. Since air has a relatively high electrical resistance value, the first wire WR1 is at a higher potential than the grid GR, but the moment the leak occurs is close to the short circuit between the first wire WR1 and the grid GR. In this state, the voltage of the grid GR slightly increases. However, since the third power supply PS3 connected to the grid GR is a power supply that performs constant voltage control, it quickly settles to a predetermined voltage. In the photoconductor PC, when the leak occurs and the discharge of the first wire WR1 is stopped, the electron flow rate from the corona charging total SC decreases, so that the surface potential cannot be increased to a predetermined value. However, this is gradually eliminated by reducing the imaging linear velocity so that the amount of electrons per unit time falling per unit area approaches the state before the discharge of the first wire WR1 is stopped. At this time, as shown in FIG. 12, by increasing the amount of discharge from the second wire WR2 in which the discharge is not stopped (S332), even if the amount of reduction in the imaging linear velocity is small, the amount falls per unit area. The amount of electrons per unit time can be brought close to the state before the discharge of the first wire WR1 is stopped.

  Even when the power supply PS1 stops power supply due to a low voltage abnormality of the first wire WR1, as shown in FIG. 13, by increasing the amount of discharge from the second wire WR2 where the discharge is not stopped (S332), Even if the amount of decrease in the image linear velocity is small, the amount of electrons per unit time falling per unit area can be brought close to the state before the discharge of the first wire WR1 is stopped.

  Even when the power supply PS1 stops power supply due to a high voltage abnormality of the first wire WR1, as shown in FIG. 14, by increasing the amount of discharge from the second wire WR2 where the discharge is not stopped (S332), Even if the amount of decrease in the image linear velocity is small, the amount of electrons per unit time falling per unit area can be brought close to the state before the discharge of the first wire WR1 is stopped.

  The content of “WR2 continuation processing” S39 is the same as the content of “WR1 continuation processing” S33, but PS2 output up is read as PS1 output up. When the “WR1 continuation process” S33 is executed, the lower bit of the modification instruction data Cac having a 2-bit configuration is set to “1”. That is, the WR1 designation data is stored in the data Cac. When the “WR2 continuation process” S39 is executed, the upper bit of the modification instruction data Cac having a 2-bit configuration is set to “1”. That is, the WR2 designation data is stored in the data Cac.

  Then, the controller 70 is notified of the abnormality of the corona charger, and the controller 70 notifies the external service center (service center with which the maintenance contract is made) via the communication control devices 97 and 83 (S35), and the charging abnormality occurs. If the charged surface is within the image frame surface, development and transfer for the image frame surface are stopped, and the next image start is set to the image (which was for the image frame) on the previous page. Then, the interrupt process is terminated, the process returns to the image forming process immediately before entering the interrupt process, and the image forming operation is restarted from a new PC charging process. If the charged surface where the charging abnormality has occurred is out of the image frame surface, the next image start is set to the next page image (S36, S37), and the image forming operation is restarted from a new PC charging process. (S36, S38).

  In “image formation stop” S41, if the charged surface where the charging abnormality occurs is within the surface for the image frame, the development and transfer for the surface for the image frame are stopped, and the previous imaged paper is fixed and discharged. Wait for it to complete and start the end cycle. That is, preprocessing for stopping the mechanism is started. Next, both the upper and lower bits of the modification instruction data Cac having a 2-bit configuration are set to “1” (S42). That is, the entire designation data is stored in the data Cac. Then, the controller 70 is notified of the abnormality of the corona charger, and the controller 70 notifies the external service center via the communication control devices 97 and 83 (S45), and the charged surface where the charging abnormality has occurred is used for the image frame. If it is within the plane, the next image formation start is set to the image of the previous page (for the image frame) (S44, S45), and the image formation operation is restarted from a new PC charging step. If the charged surface on which the charging abnormality has occurred is out of the image frame surface, the next image start is set to the image of the next page (S44, S46), and the process proceeds to "status reading" S3.

  That is, if there is a discharge abnormality in WR1 or WR2, the image frame on the PC on which the abnormality has occurred and the paper that has been developed and transferred halfway are processed as incomplete, and the image frame is automatically added to the image frame. Re-imaging is restarted from the addressed image, and the document or image and the number of sheets set (designated) for copying or printing by the user are automatically and continuously created (S36 to S38-return). When all the operations are completed, the process returns to “read status” S3. However, if there is a discharge abnormality in WR1 and WR2, the image frame on the PC on which the abnormality has occurred and the paper that has been developed and transferred halfway are processed as incomplete, and the image forming operation is interrupted there. Then, the process returns to the “read status” S3 (S44 to S46-S3), and the image forming operation of the original or image and the number of sheets set by the user for copying or printing is interrupted.

  Returning to “read status” S3, if the modification instruction data Cac is “WR1 designation data”, “WR2 designation data” or “whole designation data”, the CPU 91 proceeds to “charger modification” CAD.

  FIG. 7 shows an outline of the “charger modification” CAD. Here, the CPU 91 performs “WR1 recovery” S52 when the modification instruction data Cac is “WR1 designated data”, “WR2 recovery” S55 when it is “WR2 designated data”, and “Whole designated data”. "Overall recovery" S57 is executed.

  In “WR1 recovery” S52, in response to the power stop cause data Dam in the register Dam (S31 in FIG. 6) (S521), when it indicates a low voltage abnormality, the fan FN is rotated for a set time. Driven to cool the corona charger SC (S521). As a result, the ions staying between the scorotron grid (or the partition SL of the casing CH connected to the grid GR) are ventilated. When the power stop cause data Dam indicates a leak, the WR1 cleaning mechanism is driven to automatically clean the first wire WR1 (S552), and the fan FN is rotationally driven for a set time to corona charger SC. Is cooled (S523). When the high voltage abnormality is indicated, the WR1 cleaning mechanism is driven to automatically clean the first wire WR1 (S524). Next, the process proceeds to “WR1 recovery post-processing” S53, and the operation mode of the NV-RAM 95 is referred to. If it is in the “continuation priority” mode, the power supply power of the power source PS2 is increased (FIG. 6). S332), the setting of the power supply of the power source PS2 is restored (S532), i.e., the up is released, the imaging linear velocity is also restored (S533), i.e., the down is released, and the modification instruction data Cac is cleared. The stop lock of the power source PS1 is released (PS1 initialization) (S54). Then, the service center is notified of the automatic modification and its contents (S54).

  When the modification instruction data Cac is “WR2 designation data”, “WR2 recovery” S55 and “WR2 recovery post-processing” S56 are executed. These contents are the same as the above-described “WR1 recovery” S53 and “WR1 recovery post-processing” S53. However, WR1 is read as WR2, and PS2 is read as PS1.

  FIG. 8 shows the contents of the “overall recovery” S57. Here, if it corresponds to the return mode stored in the NV-RAM 95 and it is the complete return mode, the GR cleaning mechanism is driven to automatically clean the grid GR (S62). Next, the WR1 cleaning mechanism and the WR2 cleaning mechanism are driven to automatically clean the wires WR1 and WR2 (S63). Next, the FN is driven for a set time for the cooling fan (S64). When these are completed, both the upper and lower bits of the modification instruction data Cac having a 2-bit configuration are initialized to “0” (S65). That is, the data Cac is cleared.

  If the return mode is the simple return mode, the wires WR1 and WR2 are driven by driving the WR1 cleaning mechanism and the WR2 cleaning mechanism when both the wires WR1 and WR2 are abnormal in high voltage corresponding to the power stop cause data Dam. Automatic cleaning is performed (S67). If both the wires WR1 and WR2 are abnormal in low voltage, the cooling fan is driven for a set time (S64). If the wire WR1 or WR2 is leaking, the grid GR is automatically cleaned (S62), the wires WR1 and WR2 are automatically cleaned (S63), and the cooling fan is driven for a set time as in the case of complete recovery. When these are completed, both the upper and lower bits of the modification instruction data Cac having a 2-bit configuration are initialized to “0” (S65). When the complete return mode is executed, the possibility of leakage of the corona charger SC is reduced. The simple return mode shortens the correction time and speeds up the return to the steady imaging state.

  FIG. 9 shows an operation example when a leak occurs in the first wire WR1. At the moment when leakage occurs in the first wire WR1, the discharge current of the first wire WR1 instantaneously shows a significantly large value, and the voltage drops. This is because the first power source PS1 connected to the first wire WR1 is a power source that performs constant current control, so when a leak occurs, it is between the grid GR (or the casing CH and the partition SL connected thereto) and the like. This is because a discharge path is formed, and the resistance value between the first wire WR1 and the grid GR so far decreases, and the voltage decreases as the resistance value decreases according to Ohm's law. In the first power supply PS1, leakage is detected by detecting this voltage drop by the voltage detection circuit Vs1.

  The first power supply PS1 that has detected the leak stops outputting. Since air has a relatively high electrical resistance value, the first wire WR1 is at a higher potential than the grid GR, but the moment the leak occurs is close to the short circuit between the first wire WR1 and the grid GR. In this state, the voltage of the grid GR slightly increases. However, since the third power supply PS3 connected to the grid GR is a power supply that performs constant voltage control, it quickly settles to a predetermined voltage.

  In the photoconductor PC, when the leak occurs and the discharge of the first wire WR1 is stopped, the flow rate of electrons from the corona charger SC decreases, so that the surface potential cannot be increased to a predetermined value. However, this is gradually eliminated by lowering the imaging linear velocity (S333 / S334) to bring the amount of electrons per unit time falling per unit area closer to the state before the discharge of the first wire WR1 is stopped. When the state of the first wire WR1 is recovered by the recovery operation (S522, S523) performed after the discharge is stopped, the discharge from the first power source PS1 to the first wire WR1 is started again, and the normal image forming operation is restored. To do.

  FIG. 10 is an operation example when it is detected that there is a risk of leakage (leak precursor) due to the discharge voltage decreasing to a predetermined value (low voltage abnormality) in the first wire WR1. Ions generated when electrons emitted from the first wire WR1 due to corona discharge collide with air molecules stay between the first wire WR1 and the grid GR (and the casing CH and the partition SL connected thereto). As a result, the current resistance is reduced by decreasing the insulation resistance of the air, thereby causing leakage. Before the leak occurs, the discharge voltage of the first wire WR1 gradually decreases due to the decrease in the air resistance. The operation example in this figure shows a case where a low voltage abnormality that is a precursor of the leak occurs.

  When the discharge voltage of the first wire WR1 reaches a predetermined value (low voltage abnormal value), the first power supply PS1 determines that there is a risk of leakage and stops the discharge. When the discharge of the first wire WR1 is stopped, the photoconductor PC has a surface potential that cannot be increased to a predetermined value because the electron flow rate from the corona charging total SC decreases. However, this is gradually eliminated by lowering the imaging linear velocity (S333 / S334) to bring the amount of electrons per unit time that falls per unit area closer to the state before discharge stop of the discharge stop WR1. When the state of the first wire WR1 is recovered by the recovery operation (S521) performed after the discharge is stopped, the discharge from the first power source PS1 to the first wire WR1 is started again, and the normal image forming operation is restored.

  FIG. 11 is an operation example when it is detected that there is a risk of leakage in the first wire WR1 due to the discharge voltage increasing to a predetermined value (high voltage abnormality). Discharge resistance increases when dust such as paper dust, dust, and toner floating in the machine adheres to the first wire WR1, and the discharge voltage of the first wire WR1 increases to destroy the air insulation. This shows a case where a high voltage abnormality that is a precursor is occurring.

  As the discharge resistance increases due to adhesion of dust or the like, the discharge voltage of the first wire WR1 gradually increases. When this value reaches a predetermined value, the first power supply PS1 determines that there is a risk of leakage and stops discharging. When the discharge of the first wire WR1 is stopped, the photoconductor PC has a surface potential that cannot be increased to a predetermined value because the electron flow rate from the corona charging total SC decreases. However, this is gradually eliminated by lowering the imaging linear velocity (S333 / S334) to bring the amount of electrons per unit time falling per unit area closer to the state before the discharge of the first wire WR1 is stopped. When the state of the first wire WR1 is recovered by the recovery operation (S524) performed after the discharge is stopped, the discharge from the first power source PS1 to the first wire WR1 is started again, and the normal image forming operation is restored.

  FIG. 12 shows an operation example when a leak occurs in the first wire WR1. The difference from the previous example (FIG. 9) is that while the discharge from the first wire WR1 is stopped, the discharge current of the remaining second wire WR2 is increased to minimize the amount of reduction in the imaging linear velocity. By doing so, the decrease in productivity of the image forming apparatus is minimized. The first power supply PS1 stops outputting when a leak is detected. In the photoconductor PC, when the leak occurs and the discharge of the first wire WR1 is stopped, the electron flow rate from the corona charging total SC decreases, so that the surface potential cannot be increased to a predetermined value. However, this is gradually eliminated by lowering the imaging linear velocity (S333 / S334) to bring the amount of electrons per unit time falling per unit area closer to the state before the discharge of the first wire WR1 is stopped. At this time, by increasing the amount of discharge from the second wire WR2 in which the discharge is not stopped (S332), the amount of electrons per unit time that falls per unit area can be reduced even if the amount of decrease in the imaging linear velocity is small. The first wire WR1 can be brought close to the state before the discharge is stopped. When the state of the first wire WR1 is recovered by the recovery operation (S522, S523) performed after the discharge is stopped, the discharge from the first power source PS1 to the first wire WR1 is started again, and at the same time, the discharge of the second wire WR2 is started. By returning the amount to the normal value, the normal image forming operation is restored.

  FIG. 13 shows an operation example when it is detected that there is a risk of leakage in the first wire WR1 because the discharge voltage has decreased to a predetermined value. The difference from the previous example (FIG. 10) is that while the discharge from the first wire WR1 is stopped, the discharge current of the remaining second wire WR2 is increased to minimize the amount of reduction in the imaging linear velocity. By doing so, the decrease in productivity of the image forming apparatus is minimized. When the first power supply PS1 stops supplying power and the discharge of the first wire WR1 stops, the electron flow rate from the corona charging total SC decreases in the photoconductor PC, so that the surface potential cannot be increased to a predetermined value. However, this is gradually eliminated by lowering the imaging linear velocity (S333 / S334) to bring the amount of electrons per unit time falling per unit area closer to the state before the discharge of the first wire WR1 is stopped. At this time, by increasing the amount of discharge from the second wire WR2 in which the discharge is not stopped (S332), the amount of electrons per unit time that falls per unit area can be reduced even if the amount of decrease in the imaging linear velocity is small. The first wire WR1 can be brought close to the state before the discharge is stopped. When the state of the first wire WR1 is recovered by the recovery operation (S521) performed after the discharge is stopped, the discharge from the first power source PS1 to the first wire WR1 is started again, and at the same time, the discharge amount of the second wire WR2 is set to normal. When the value is lowered to the normal value, the normal image forming operation is restored.

  FIG. 14 shows an operation example when it is detected that there is a risk of leakage in the first wire WR1 because the discharge voltage has increased to a predetermined value. The difference from the previous example (FIG. 11) is that while the discharge from the first wire WR1 is stopped, the discharge current of the remaining second wire WR2 is increased and the amount of reduction in the imaging linear velocity is minimized. By doing so, the decrease in productivity of the image forming apparatus is minimized. When the first power supply PS1 stops supplying power and the discharge of the first wire WR1 stops, the electron flow rate from the corona charger SC decreases in the photoconductor PC, so that the surface potential cannot be increased to a predetermined value. However, this is gradually eliminated by lowering the imaging linear velocity (S333 / S334) to bring the amount of electrons per unit time falling per unit area closer to the state before the discharge of the first wire WR1 is stopped. At this time, by increasing the amount of discharge from the second wire WR2 in which the discharge is not stopped (S332), the amount of electrons per unit time that falls per unit area can be reduced even if the amount of decrease in the imaging linear velocity is small. The first wire WR1 can be brought close to the state before the discharge is stopped. If the state of the first wire WR1 is recovered by the recovery operation (S524) performed after the discharge is stopped, the discharge from the first power source PS1 to the first wire WR1 is started again, and at the same time, the discharge amount of the second wire WR2 is normally set. When the value is lowered to the normal value, the normal image forming operation is restored.

  FIG. 15 shows the configuration of the power supplies PS1 to PS3 according to the second embodiment of the present invention. These power supplies feed a positive voltage corona charging power to the corona charger SC. The first power source PS1 connected to the first wire WR1 of the corona charger SC is a switching type power source that performs constant current control, and the drive circuit DR1 uses the output current value detected by the current detection circuit Is1 to perform feedback control. Thus, constant current control is performed so that the magnitude of the discharge current from the first wire WR1 becomes a predetermined value. Since the forward direction of the electrical connection of the diode D1 of the power supply PS1 is opposite to that of the diode D1 of the first embodiment, the first power supply PS1 of the second embodiment shown in FIG. 15 generates a positive voltage.

  The second power source PS2 connected to the second wire WR2 of the corona charger SC is also a switching type power source that performs constant current control, and from the second wire WR2 by feedback of the output current value from the current detection circuit Is2. The drive circuit DR2 performs control so that the magnitude of the discharge current becomes a predetermined value. The second power supply PS2 also generates a positive voltage.

  The third power source PS3 connected to the grid GR of the corona charger SC is a shunt regulator (dropper) type power source that performs constant voltage control, and the grid GR is fed back by feedback of the output voltage detection signal from the voltage detection circuit Vs3. The drive circuit DR3 performs voltage feedback control (constant voltage control) so that the potential becomes a predetermined value. The third power supply PS3 generates a positive voltage.

  In order to generate a voltage using the flow of the discharge current from the first wire WR1 and the second wire WR2 into the grid GR, the third power source is provided if both the outputs of the first power source PS1 and the second power source PS2 are cut off. The output of PS3 stops. However, it is possible to generate an output voltage to the grid GR unless the discharge of all the discharge means is stopped.

  Other hardware and functions of the second embodiment are the same as those of the first embodiment described above, except for the mechanism and function changes accompanying positive charging of the photosensitive drum PC.

1 is a longitudinal sectional view of a multi-function full-color copying machine equipped with a sheet transfer device according to an embodiment of the present invention. FIG. 2 is a block diagram showing an outline of an image processing system of the copying machine shown in FIG. 1. It is an enlarged plan view which shows the external appearance of the operation board shown in FIG. FIG. 2 is a block diagram illustrating a configuration of one set of four corona chargers SC illustrated in FIG. 1 and power supplies PS1 to PS3 that supply power thereto. It is a flowchart which shows the outline | summary of the system control of the controller 71 shown in FIG. 2, and modification of the corona charger of CPU91. It is a flowchart which shows the content of the interruption process in response to abnormality generation of the corona charger SC of CPU91 shown in FIG. It is a flowchart which shows the content of the "charger correction" CAD shown in FIG. 5 which CPU91 shown in FIG. 2 performs. It is a flowchart which shows the content of "total recovery" S57 shown in FIG. FIG. 5 is a time chart showing a first example of changes in voltage, current, and image forming linear velocity of each part of the corona charger when a leak occurs in the first wire WR1 shown in FIG. 4; 6 is a time chart showing a first example of changes in voltage, current, and image forming linear velocity of each part of the corona charger when a low voltage abnormality occurs in the first wire WR1 shown in FIG. 6 is a time chart showing a first example of changes in voltage, current, and image forming linear velocity of each part of the corona charger when a high voltage abnormality occurs in the first wire WR1 shown in FIG. 6 is a time chart showing a second example of changes in voltage, current, and image forming linear velocity of each part of the corona charger when a leak occurs in the first wire WR1 shown in FIG. FIG. 5 is a time chart showing a second example of changes in voltage, current, and image forming linear velocity of each part of the corona charger when a low voltage abnormality occurs in the first wire WR1 shown in FIG. FIG. 5 is a time chart showing a second example of changes in voltage, current, and image forming linear velocity of each part of the corona charger when a high voltage abnormality occurs in the first wire WR1 shown in FIG. It is a block diagram which shows the structure of the power supplies PS1-PS3 of 2nd Example of this invention.

Explanation of symbols

10: Operation board 20: Color document scanner 30: Automatic document feeder 40: Color printer 41: Transfer belt 42: Transfer roller 43: Optical writing unit SC: Corona charger WR1, WR2: Corona discharge wire GR: Grid SL: Partition CH: Casing PS1 to PS3: Power supply 45: Conveying belt 46: Fixing unit 47: Registration roller pair 51-53: Paper feed tray PCM: Personal computer PBX: Exchanger PN: Communication line 200: Power supply circuit

Claims (14)

A corona discharger having a plurality of discharge means facing the surface of the member to be charged and having a partition between the plurality of discharge means;
Each has a function of supplying corona discharge power to each discharge means, a function of stopping the power supply, a function of changing the power supply according to a change instruction, and a function of restarting power supply of the corona discharge power by canceling the stop. Have multiple charging power supplies;
A discharge abnormality detecting means for stopping the power supply of the charging power supply for detecting a discharge abnormality of each discharge means and supplying power to the discharge means that has caused the discharge abnormality; and
A corona charging device comprising: control means for instructing another charging power source to increase the power supply when one of the plurality of charging power sources stops power supply due to abnormal discharge.   The corona charging device according to claim 1, wherein the discharge abnormality includes a leakage and a voltage abnormality in which no leakage occurs. Charge carrying medium;
The corona charging device according to claim 1 or 2, wherein the surface of the charge carrying medium is charged;
Latent image forming means for forming a static latent image of an image represented by the image data by discharging the charge surface of the charge carrying medium corresponding to the image data;
Means for applying a developer to the electrostatic latent image to develop a visible image; and
An image forming apparatus comprising: means for transferring the visible image onto a sheet.   4. The image forming apparatus according to claim 3, wherein the control unit reduces the moving speed of the charge carrying medium when one of the plurality of charging power supplies stops power supply due to discharge abnormality. 5.   The image forming apparatus according to claim 4, wherein the control unit stops transfer to the paper when the charging power supply stops power supply due to abnormal discharge.   When the charging power supply stops power supply due to abnormal discharge, the control means determines the next image after the formation of the electrostatic latent image as an image and charges the surface of the charge carrying medium. The image forming apparatus according to claim 3, wherein an image forming operation following the process is performed.   When the designated image forming operation is completed, after the set time, the control means cancels the suspension of the charging power supply that has stopped power supply due to the discharge abnormality, and instructs the charging power supply that has instructed to increase the power supply power. The image forming apparatus according to claim 6.   The image forming apparatus according to claim 7, wherein the control unit drives an air conditioning unit that exhausts the gas of the corona discharger during the set time.   When the designated image forming operation is completed, the control means drives the cleaning mechanism of the corona discharger.When the cleaning is completed, the control unit releases the suspension of the charging power supply that has stopped feeding due to the discharge abnormality, The image forming apparatus according to claim 6, wherein the instruction of the charging power supply instructed to increase the supply power is canceled.   The control means interrupts the image forming operation when two or more of the plurality of charging power supplies are stopped due to discharge abnormality, and the next to the image after the formation of the electrostatic latent image is completed. The step of setting the image of the image, and after a set time, canceling the stop of the charging power supply that stopped power supply due to the discharge abnormality, and charging the surface of the charge carrying medium of the image determined for the image formation is as follows: The image forming apparatus according to claim 3, wherein an image forming operation is performed.   The image forming apparatus according to claim 10, wherein the control unit drives an air conditioning unit that exhausts the gas of the corona discharger during the set time.   The control means interrupts the image forming operation when two or more of the plurality of charging power supplies are stopped due to discharge abnormality, and the next to the image after the formation of the electrostatic latent image is completed. When the cleaning mechanism of the corona discharger is driven and the cleaning is completed, the suspension of the charging power source that stopped power feeding due to the discharge abnormality is released, and the image of the image determined for the imaging is determined. The image forming apparatus according to claim 3, wherein the image forming operation is performed following the step of charging the surface of the charge carrying medium.   13. The image forming apparatus according to claim 3, further comprising: a communication unit configured to communicate a power supply stop due to the discharge abnormality to a service center through communication.   14. The image forming apparatus according to claim 7, further comprising: a communication unit configured to communicate with a service center by communication the release of the charging power source that has stopped supplying power due to the discharge abnormality.

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